Searching for the missing pieces of climate change communication

What’s in a number?

For those who didn’t heard the news yet, since shortly CO2 levels in Mauna Loa starting to reach 400 ppm. It was hailed as an important number, some even talked about a tipping point. So I thought it would be an interesting project to look into this a bit more in detail and find how much is too much when CO2 is concerned.

First things first, the 400 ppm level. I read about it in a paper last Tuesday. I could trace back the origin to a media alert by Christina Figueres, executive Secretary of UNFCCC.

“With 400 ppm CO2 in the atmosphere, we have crossed an historic threshold and entered a new danger zone. The world must wake up and take note of what this means for human security, human welfare and economic development. In the face of clear and present danger, we need a policy response which truly rises to the challenge. We still have a chance to stave off the worst effects of climate change, but this will require a greatly stepped-up response across all three central pillars of action: action by the international community, by government at all levels, and by business and finance.”

“Historic threshold”, “new danger zone”, “in the face of clear and present danger”! No hyperboles were spared in this one. But hey, we lucky people, we still have a chance to evade this bullet!

The big question we started with: how much is too much? I remember that this is not the first time the media reported major tipping points. I remembered values of 350 ppm, 650 ppm and the pre-industrial level. Picture my surprise when I hit Google with some search terms and found loads of links to statements which involves numerous CO2 tipping points. Next you will find one or two examples of each level. There are loads more to be found on the internet.

Let’s start with a very known level. There is of course the 350 org organization, which states 350 ppm is the upper limit and we should return to that to be on the safe side.

350 means climate safety. To preserve our planet, scientists tell us we must reduce the amount of CO2 in the atmosphere from its current level of 392 parts per million to below 350 ppm. But 350 is more than a number-it’s a symbol of where we need to head as a planet.

2. Urgent reduction of atmospheric CO2 to a safe level of about 300 ppm as recommended by leading climate and biological scientists.

These are probably levels from almost 70 years ago! Even that seems too high. What about 280 ppm? Earth was, ahum, “in balance” with that, so it would be straight forward to aim for that level. According to State of Nature

If burning fossil fuels like coal and oil during industrialization has created the mess we’re in with climate change, it seems only logical that we should aim for pre-industrial levels of atmospheric CO2 of 280 ppm.

“Avoiding Dangerous Climate Change: A Scientific Symposium on Stabilisation of Greenhouse Gases” was a 2005 international conference[16] that examined the link between atmospheric greenhouse gas concentration, and the 2 °C (3.6 °F) ceiling on global warming thought necessary to avoid the most serious effects of global warming. Previously this had generally been accepted as being 550 ppm

560 is also a real nice number (twice the pre-industrial level of 280). On the climate avenue website:

It is calculated that if the carbon dioxide concentration reaches 560 ppm, the world will be in great danger.

The Golden Rules Case puts CO 2 emissions on a long-term trajectory consistent with
stabilizing the atmospheric concentration of greenhouse-gas emissions at around
650 parts per million, a trajectory consistent with a probable temperature rise of more
than 3.5 degrees Celsius (°C) in the long term, well above the widely accepted 2°C target.

But it doesn’t stop there: what about tripling or quadrupling the pre-industrial level (840 – 1120 ppm)? NY Times reports:

Some experts think the level of the heat-trapping gas could triple or even quadruple before emissions are reined in.
[…]
Even if climate sensitivity turns out to be on the low end of the range, total emissions may wind up being so excessive as to drive the earth toward dangerous temperature increases

Here I stopped my search. This was a dizzying experience. So many declared tipping points and I even didn’t searched for increments of 25 yet. From 220 to 1120, that is quite a difference! Some advice for those who want to declare a new tipping point: 50 at the end is nice, but increments of 100 or increments of 280 are even better.

Why so many declared tipping points? Let’s go back to the media alert of the UNPCCC:

Governments will be meeting 3 – 14 June in Bonn for the next round of climate change talks
under the umbrella of the UNFCCC. A central focus of the talks will be negotiations to build a new
global climate agreement and to drive greater immediate climate action.

So, why 400 ppm? Well, if it is there, why not just using it? The 400 ppm is a political move, those meeting Governments will get that rubbed in to steer the negotiations into a certain direction. The other declared tipping points probably also had their specific purpose. They are probably more symbolic in nature than scientific.

Speaking of numbers with a symbolic meaning, this is the 13th post on this blog. Should I start getting nervous? 😉

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2 thoughts on “What’s in a number?”

Very interesting. The lower numbers don’t really seem to mean much other than “it would be good if we could reach these goals”, but the lack of agreement on what the dangerous Higher numbers are is a bit odd; it makes it look like nobody is very clear on anything or has enough information to make accurate predictions.